Robot singer: build your own vocaloid

Type syllables, place notes on a piano roll, and a drawn singer sings your melody with a synthesized voice. Like the first vocaloids, only in your browser.

What you’ll get

This mission is for a paid Gemini account (Google AI Pro): a stronger model writes sound-synthesis code more reliably. The voice will sound robotic — that’s how the first singing synthesizers sounded. We tested the prompt 3 times out of 3.

Steps

Open gemini.google.com on a parent’s account with Google AI Pro and pick the strongest model (ours was Argon).

Copy the whole prompt and send it:

Make a vocaloid-like singing synthesizer in a single HTML file. Don't load anything from the internet: no Tailwind, no CDN, no fonts, no images and no libraries — only your own CSS and JavaScript inside the file. Don't save anything in the browser's storage. Build the voice in Web Audio with formant synthesis: a sawtooth oscillator with a light vibrato goes through three band-pass filters set to the formant frequencies of the vowels a, o, u, i, e; consonants are a short burst of noise before the vowel. At the top, a piano roll of 2 octaves and 16 steps: a tap places a note, and every note has a field for a syllable (for example "la", "mi"). Buttons: Play, Stop, Clear, Example (your own powerful melody in the style of stadium pop-rock, like Imagine Dragons: rhythmic "oh-oh" and "hey", a strong chorus; don't copy other people's songs, compose your own). Sliders: tempo, voice pitch, vibrato. The sound starts only after Play is pressed. At the bottom, draw an anime singer on a canvas: her mouth opens in the shape of the current vowel, and the current note lights up. Check that all variables are declared. Everything must look good on a phone. Show the result in Canvas.

Wait about a minute, click Preview, then Example and Play.
Check the AI (see the question above).
Compose your own song and click Download (sometimes it’s the Export menu) — the file opens in any browser.

Change the prompt

Change only the words, and keep the rules about the internet and Canvas.

“anime singer” → “a robot singer with antennas”
“like Imagine Dragons” → your favorite band or style: “like K-pop”, “like rap”

If it doesn’t work

No sound? Write: There's no sound after pressing Play. Find and fix the error in Web Audio.
The voice just hums? Write: The vowels sound the same. Make the formants for a, o, u, i, e more different from each other.
No Preview button? Write: Show the result in Canvas.